The first four terms of a sequence are shown below:

9, 5, 1, −3

Which of the following functions best defines this sequence?

A.) f(1) = 9, f(n + 1) = f(n) − 4; for n ≥ 1
B.) f(1) = 9, f(n + 1) = f(n) + 4; for n ≥ 1
C.) f(1) = 9, f(n + 1) = f(n) − 5; for n ≥ 1
D.) f(1) = 9, f(n + 1) = f(n) + 5; for n ≥ 1

Question

The first four terms of a sequence are shown below:

9, 5, 1, −3

Which of the following functions best defines this sequence?

 A.) f(1) = 9, f(n + 1) = f(n) − 4; for n ≥ 1
 B.) f(1) = 9, f(n + 1) = f(n) + 4; for n ≥ 1
 C.) f(1) = 9, f(n + 1) = f(n) − 5; for n ≥ 1
 D.) f(1) = 9, f(n + 1) = f(n) + 5; for n ≥ 1

victoriasushchik · Answer

f(x)_1 = 9
f(x)_2 = f(x)_1 - 4
so your sequence will be 9, 5, 1, -3, -7, -11...

victoriasushchik · Answer

so your answer will be : f(1) = 9, f( n + 1 ) = f(n) - 4, for n > 1

pawanyadav · Answer

You can check 
9-5=4
5-1=4
1-(-3)=4
So every next term is 4 less than previous term.

anonymous · Answer

$$common~difference=-4$$$$f(n+1)=n-4$$yep :)

victoriasushchik · Answer

yep that's right!

celinegirl · Answer

Thank you!